Presence of d-dimers in human cerebrospinal fluid (CSF) has been used to assess fibrinolytic activity in CNS disease; C-reactive protein (CRP) has also been associated with meningeal inflammation. This study investigated d-dimers and CRP as markers for inflammatory CNS disease in dogs. Included were 169 dogs with neurologic disorders (eg, steroid-responsive meningitis arteritis [SRMA], neoplasia, spinal compressive disorders, other inflammatory neurologic disease, idiopathic epilepsy, noninflammatory neurologic disease); 7 healthy beagles, and 7 dogs with systemic inflammatory diseases (SIDs) not involving the CNS. Paired blood and CSF samples were collected and d-dimer and CRP concentrations measured and compared. CSF was also analyzed for total nucleated cell count, RBC count, and protein concentration. Elevated d-dimer levels were present in 79 (43%) CSF samples. CSF d-dimer concentrations were higher in dogs with SRMA than in other groups. There was no correlation between blood and CSF d-dimer concentrations. CRP was detected in 182 (99.5%) samples. Intrathecal CRP concentrations were elevated in dogs with SRMA and those with nonneurologic SIDs. There was a high correlation between blood and intrathecal CRP concentrations.

CRP may cross the blood-brain barrier and appears to have poor diagnostic specificity in differentiating neurologic vs nonneurologic disease. CSF d-dimer concentrations may be highly specific for severe meningeal inflammation in dogs and considered a diagnostic marker for SRMA.

Source
Fibrinolytic activity in cerebrospinal fluid of dogs with different neurological disorders. De la Fuente C, Monreal L, Cerón J, et al. JVIM 26:365-1373, 2012.

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